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DPTIPS: Maximize Catalyst value with Auto Replication Sync (ARS)

Jim Turner

Overview
You have a primary data center (PDC) and a secondary data center (SDC).  You have an HPE StoreOnce appliance at each center as well as an HPE Data Protector cell manager (CM) at each location.  So far, so good, right?  But where do we go from here?

With two data centers and BURA resources at each, what we want is the ability to begin immediate recovery of production data at the secondary site should the primary site become unavailable.  Let's say your PDC does go dark.  You're left with your SDC and replicas of all your backup data.  Historically your data recovery would be delayed by the need to import catalog details for all of the replica data.  Here my friends is where a fairly new feature in Data Protector is worth its weight in gold:  Auto Replication Sync

What I share below is a case study of the following implementation.

  • Primary and replica B2D devices and associated Catalyst stores on the PDC CM.
  • A B2D device on the SDC CM that maps to the PDC replica.
  • Importing the SDC CM as a foreign cell manager in the PDC CM's list of clients.
  • A PDC backup specification that writes to the primary Catalyst store at the PDC.
  • A PDC post-backup copy specification that replicates to the Catalyst store at the SDC.
  • Configuring the post-backup copy to notify the foreign CM which triggers the ARS.
  • Watch it all work!

(One programming note:  My image editing skills are laughably insufficient.  Some screen shots have site-specific information altered or removed.  Thus the same parts of the GUI in your environment may look slightly different.)

B2D devices and Catalyst stores

Primary DC
When we created the backup to disk (B2D) devices on the PDC CM, we also created the corresponding Catalyst store on each appliance.  Although both of these B2D devices are local to the PDC CM, only the primary Catalyst store lives on the PDC StoreOnce appliance.  The replica store lives on the SDC StoreOnce appliance and accessed by the PDC CM's B2D device for the replica.

Secondary DC
On the SDC CM we created a corresponding B2D device that maps to the replica store on the SDC StoreOnce appliance.  What we have then is one common replica store on the SDC StoreOnce appliance that is accessed by both a B2D device at the PDC and a separate B2D device at the SDC.

 

ARS01.jpg

Importing a foreign cell manager
Utilizing Automatic Replication Synchronization (ARS) requires that the identity of the SDC CM be made known to the PDC CM.  This is done by importing with a new client type called "Foreign Cell Manager".

Begin the import like you would with any other client by right-clicking the Clients folder and selecting Import Client.  Supply the FQDN of the secondary CM and set the type to Foreign Cell Manager..

ARS02.jpg

Click the Finish button at lower right, and now your primary CM knows the identity of your secondary CM.

Backup Specification
The backup spec is fairly ordinary.  Our destination is of course the B2D device on the PDC CM that maps to the local Catalyst store on the PDC StoreOnce appliance.  Note that we are taking advantage of source-side dedupe.

ARS03.jpg

Copy Specification
The basics
We created our post-backup copy spec like most others.  First we selected the backup spec to trigger on then the source B2D device to search within.  Options for selecting only protected objects and/or objects with a copy count less than 1 are not relevant to our post-backup copy because the objects being copied are only the ones just created by the backup.

Gateway replacement
Just a note here to remind you that implicit source-side gateways are incapable of sending API calls to StoreOnce for low-bandwidth replication (LBR).  Since our backup job used source-side dedupe, we must replace the implicit gateway with an explicit gateway in the post-backup copy spec on the PDC CM.

On the Source tab of your post-backup copy spec, right-click the source-side device used for the backup and select Change Device.

ARS04.jpg

In the Select New Device dialog, locate and select the explicit gateway associated with the same store as our implicit source-side gateway used during the backup.

ARS05.jpg

Click the OK button, and you'll be returned to your copy spec properties with a confirmation that the original source device was replaced with your choice.

ARS06.jpg

Our destination is the PDC CM's B2D device that maps to the replica store at the SDC, namely PRDFS01_REP.  We are using a local B2D device to communicate with a remote Catalyst store.

ARS specifics
On the Options tab we check the "Use replication" box which triggers LBR and prevents data from being rehydrated and passed through hosts.  Note just below that we have a new "Replicate to a foreign cell" box to check.

ARS07.jpg

Pause for a moment and remember that we have a PDC CM B2D device that writes to a replica Catalyst store on the SDC StoreOnce appliance.  We also have an SDC CM B2D device that accesses the very same replica Catalyst store on the SDC StoreOnce appliance.

ARS09.jpg

Hopefully that keeps things clear as we return to our PDC copy spec and look at the new "Foreign Destination" tab where we have the B2D device from the SDC CM that maps to the same SDC store as the destination B2D device on the PDC CM.

ARS08.jpg

That's the last step.  Now it's time to kick off the backup and see if everything works as advertised.

Putting it all together
Our backup runs without incident.  The end of the backup session triggers the post-backup replication job which again is nothing remarkable at first, but let's take a closer look at session messages specific to LBR and more importantly ARS.

The first ARS-flavored change you will see is a message from the Copy Session Manager (CSM) very near the start of the session indicating Automatic Replication Synchronization has been invoked.

[Normal] From: CSM@pdc-cm.domain.loc "PRDFS01 Rep Job"  Time: 2/23/2016 8:00:48 PM
                Automated Replication Synchronization started.

That is followed by the usual litany of media agents starting and completing as API calls are made to the StoreOnce appliances at each site from the PDC CM gateway.

Here's where things get interesting.  Since we opted to notify a foreign cell manager and we identified the store on the foreign cell manager to update, look what happens after the normal part of the replication completes:

[Normal] From: MSM@sdc-cm.domain.loc "PRDFS01_REP_SDC-CM"  Time: 2/23/2016 8:25:09 PM
                Media session 2016/02/23-23 started.

[Normal] From: MSM@sdc-cm.domain.loc "PRDFS01_REP_SDC-CM"  Time: 2/23/2016 8:25:09 PM
                Automated Replication Synchronization started by user DP_SVC.DOM@sdc-cm.domain.loc.

Yes, indeed!  CSM on the PDC CM has reached out and started a Media Session Manager (MSM)  on the SDC CM to import catalog details from Catalyst media in the replica store.  By no small coincidence the media to import is the exact list of media freshly updated from the backup that triggered the now-running replication job.

[Normal] From: MSM@sdc-cm.domain.loc "PRDFS01_REP_SDC-CM"  Time: 2/23/2016 8:25:10 PM
                Data Protector foreign medium "2300d40a:56cd1ce6:082c:02a9" found.

[Normal] From: MSM@sdc-cm.domain.loc "PRDFS01_REP_SDC-CM"  Time: 2/23/2016 8:25:21 PM
                Importing session into database:  
                    SessionID:   2016/02/23-23  
                    Owner:       DOM\DP_SVC@sdc-cm.domain.loc  
                    Start time:  2/23/2016 8:00:50 PM

[Normal] From: MSM@sdc-cm.domain.loc "PRDFS01_REP_SDC-CM"  Time: 2/23/2016 8:25:21 PM
[65:98]                 Duplicate session ID found in the database.
                New session was created by DP_SVC.DOM@sdc-cm.domain.loc.
                    New sessionID:   2016/02/23-24

MSM burns through all necessary replica media and imports the session and catalog details contained thereon.

The very last step of replication with ARS involves media in the replica B2D device at the PDC being exported such that the replica store appears empty when viewed from the PDC CM.  This will be explained momentarily.

The results
When replication with ARS is complete, here is the end state:

  • Catalyst store PRDFS01 on the PDC StoreOnce appliance contains the source media.
  • B2D device PRDFS01 on the PDC CM knows about the source media at the PDC.
  • Catalyst store PRDFS01_REP on the SDC StoreOnce appliance contains the replica media.
  • B2D device PRDFS1_REP on the SDC CM knows about the replica media at the SDC.
  • B2D device PRDFS1_REP on the PDC CM is empty.  No media is visible.

 

ARS10.jpg

This means that the PDC CM can restore from its local PDC Catalyst store, and the SDC CM can restore from its local SDC Catalyst store replica with no delay whatsoever.  Total loss of either site will not delay the start of recovery operations!

I have been asked why replicated media is exported from the PDC CM's replica B2D device.  That is because you don't want two separate cell managers knowing about common media.  One CM could make a change after ARS, and the other CM would not know anything of the change thus knocking the catalog data out of sync.

That's it, then.  I hope this article proves useful for those seeking to take advantage of HPE Data Protector's advanced Auto Replication Sync functionality with HPE's StoreOnce appliances.  Please leave a comment if you have questions or see a way for this material to be improved.

Dependencies
ARS requires DP 9.04 or later.  Your standby CM User List needs to include an admin user that matches the DP user running the replication job on the primary CM.  ARS only works with Catalyst stores.  Legacy VTL and NAS replicaiton are unchnged.

Acknowledgements
A big THANK YOU to Scott McCallum in Calgary, AB for his collaboration and advice in creating this article.  It would not have been possible without him.


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About the Author

Jim Turner

Jim is a multi-disciplined engineering professional with 30 years of electronic and systems experience. For the past 17 years, Jim’s primary focus has been enterprise backup, recovery, and archiving (BURA). As an HPE Master Technologist, he is recognized as a global authority on HPE Data Protector, HPE StoreOnce, and the proper integration of both. Jim's consulting has stretched over 370k miles and 151 unique locations in North America during his 9 years with HP(E). When not traveling, Jim resides in Edmond, OK with his wife and two dogs.

Comments
Jean-Yves LE Bouche

Hello Jim,

Thanks for this very helpful article.

I have a question here. B2D devices in Data Protector documentation represent Data Protector sofware deduplication devices. In the screenshots you gave, devices looks like classical StoreOnce devices. Can we mix the two kinds of devices ? For example replicate a Software B2D device to a catalyst store on a storeonce ?

 

Ken Krubsack

Jim, I've been wondering how the auto DR in DP 9 worked.

If this works as advertised, it just obsoleted the script we wrote back in early 2015.

Ken

Johnc_3

Hi Jim,

 

How does the DP licensing work for this; would you require Advanced Backup To Disk licenses for DP at the SDC, even though the data on the SDC StoreOnce is a replica of the data at the PDC and would never be used unless a disaster occurred?

 

John

Vince Laurent

Is there a way to set this up before having the second CM?  I have 3 StoreOnce systems (4500) and will have a PDC, SDC, TDC (out of region).  Will not have a SDC CM till the end of the year.  What might I have to do differetnt?

Hassan Abdul Kader

Hi Jim,

The copy backup is configured as per the guidence. The replication starts ok but i ends with failure with the beliw error message.

[60:1055] Unable to start MSM for import on machine 

Please advise, what could be the issue ?

Thanks,

Hassan

Jim Turner

Hello Hassan Abdul Kader,

Please ensure that the same AD user is starting CRS on both cell managers.  Further, ensrue that particular AD user is an admin user in DP's user list on both the primary and foreign cell manager.

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